1. Field of the invention
This invention relates to a system for particle analysis and, more particularly, to a fluidic system that uses a flexible diaphraghm valve.
2. Description of the Prior Art
Systems for counting and analyzing particles suspended in a fluid find application in a variety of areas, particularly medical diagnostics. An early disclosure of an electrical method for detecting and counting particles in a fluid, where the fluid and particles have different electrical conductivities, was made in U.S. Pat. No. 2,656,508, issued Oct. 20, 1953, to W. H. Coulter. Since then, a large number of related patents and publications have appeared that involve improvements and/or refinements of the Coulter technique (see, e.g., U.S. Pat. No. 3,015,775, issued Jan. 2, 1962, to W. H. Coulter et al.). Basically, the technique involves monitoring the electrical impedance across a narrow gap as a dilute sample passes through the gap. The presence of a particle is indicated by a change in the impedance.
A valve that is useful in biological fluid handling systems was disclosed in U.S. Pat. No. 4,304,257, issued Dec. 8, 1981, to M. E. Webster. That valve involves two mating surfaces, one firm and one flexible. In one of the surfaces are channels, separated by lands that are coincident with the surface. For each pair of channels and the land that separates them, an actuator moves the flexible surface between one position, in which the flexible surface is sealed against the firm surface to prevent flow between the channels, and a second position, in which the flexible surface is spaced away from the first position to permit flow between the channels. The firm surface may be provided by a transparent material having a planar surface.
A system for analyzing a biological fluid was disclosed in U.S. Pat. No. 4,283,262, issued Aug. 11, 1981, to A. D. Cormier et al. The system comprises an analysis chamber, a measuring system connected to the analysis chamber, a flow network for connecting an inlet and an auxiliary fluid reservoir to the analysis chamber, and a pump between the analysis chamber and an outlet. The system may include valves of the type disclosed by Webster.